Update draggable to 2.0-SNAPSHOT

[jclariviere]

Droppable was using draggable 1.0.4. The 2.0 version on Arcbees had some changes in it's interface that was breaking Droppable. See this issue : https://github.com/ArcBees/gwtquery-droppable-plugin/issues/2

Droppable version 1.0.5 to 1.0.8 didn't seem to match the trunk from googlecode, and it seems the Github's initial version was using 1.0.8. So I checked out the initial Github version, applied the Element -> DragContext changes, then rebased on master.

[christiangoudreau]

GJ! LGTM

@jDramaix needs to review though.

Also, would be great to do a PR to move to 4 spaces instead of 2

[meriouma]

Few nits, otherwise good job, LGTM

[jDramaix]

If the examples work, LGTM